linux-kernel - [PATCH][next] net/mlx4_en: Replace fake flex-array with flexible-array member

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Message-ID: <ZAZ8mNbphtPyZWM6@work>
Date:   Mon, 6 Mar 2023 17:51:52 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Tariq Toukan <tariqt@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] net/mlx4_en: Replace fake flex-array with
 flexible-array member

Zero-length arrays as fake flexible arrays are deprecated and we are
moving towards adopting C99 flexible-array members instead.

Transform zero-length array into flexible-array member in struct
mlx4_en_rx_desc. 

Address the following warnings found with GCC-13 and
-fstrict-flex-arrays=3 enabled:
drivers/net/ethernet/mellanox/mlx4/en_rx.c:88:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:149:30: warning: array subscript 0 is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:127:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:128:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:129:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:117:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
drivers/net/ethernet/mellanox/mlx4/en_rx.c:119:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].

Link: https://github.com/KSPP/linux/issues/21
Link: https://github.com/KSPP/linux/issues/264
Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index 544e09b97483..034733b13b1a 100644
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -323,7 +323,7 @@ struct mlx4_en_tx_ring {
 
 struct mlx4_en_rx_desc {
 	/* actual number of entries depends on rx ring stride */
-	struct mlx4_wqe_data_seg data[0];
+	DECLARE_FLEX_ARRAY(struct mlx4_wqe_data_seg, data);
 };
 
 struct mlx4_en_rx_ring {
-- 
2.34.1